The present invention relates generally to broadband communications and more particularly to rate selection procedure for channel selection in flexible wavelength division multiplexing WDM networks.
In conventional wavelength division multiplexing (WDM) optical networks, the spectrum allocation to the WDM channels (determined from the channel spacing) is fixed, and remains the same throughout the network operation. These channels are centered on standard ITU-T channel grid such as specified according to ITU-T standard G.694.1 [ITU-T]. We refer such networks as the fixed grid optical WDM networks. In the fixed grid networks, the fixed amount of spectrum is assigned to all connections irrespective of their data rates, which leads to an inefficient utilization of spectral resources (FIG. 1(a)). Such a network is rigid and cannot provide optimum spectral efficiency.
Envisioning the requirement for higher spectral efficiency to support future traffic volume, there have been several efforts for relaxing the constraints of fixed spectral allocation in the optical WDM networks, which we refer as the Flexible optical WDM networks (FWDM). The FWDM consists of optical channels supporting heterogeneous line rates using variable amount of spectrum as shown in FIG. 1(b) as opposed to the fixed grid networks.
In the fixed grid optical networks, fixed and same amount of spectrum is allocated to all channels. Thus the total required spectrum by the given set of channels can be determined as follows:Total Spectrum=Number of channels in the given set*spectrum of a channel.
Since the spectrum of all channels is fixed and the same, to minimize the total spectrum, we need to minimize the total number of channels required for the given data rate. Thus, the object of the channel selection problem is equivalent to minimize the total number of channels to support the connection. The channel selection problem in the fixed grid network can trivially solved by selecting the channels with the maximum line rate, which minimizes the total number of channels for the given data rate.
However, since the spectrum assignment to the channels in the FWDM networks is flexible, the channel selection problem becomes more general than in the fixed grid networks. The solution of the channel selection problem in the fixed grid networks may not be the solution of the channel selection problem in the FWDM networks.
For example, if an end user requests a connection of 410 Gb/s data rate from San Francisco to New York, and the FWDM network consists of multiple channels supporting 10 Gb/s, 40 Gb/s, 100 Gb/s, and 400 Gb/s line rates with the required spectrum 25 GHz, 50 GHz, 50 GHz, and 75 GHz respectively. The aforementioned solution of the channel selection problem in the fixed grid network selects the channels with maximum line rate to reduce the number of channels, which requires 2 channels, each of them with the line rate 400 Gb/s, which is the maximum among the given set of line rates, and the total required spectrum is 150 GHz. However, if we intelligently select one channel with line rate 400 Gb/s and the other channel with line rate 10 Gb/s, then the total required spectrum is reduced to 100 GHz.
So far, there is no existing solution (prior art) for the channel selection problem in the FWDM network, and we are the first one who introduce the channel selection problem, and propose the efficient procedure to solve it.
Accordingly, there is a need for an efficient channel selection in a flexible WDM (FWDM) network.